General Guide to Machining - Alloys

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The Nickel-Iron Family generally includes , TURNING ®, Alloys 42, 46, 48, and 52, Alloy 42-6 and the If cutting tools are used, try a feed of approximately magnetic shielding alloys such as MuMetal. .010” to .012” per revolution and a speed as high as 35/ FPM could probably be attained. Some of the angles on the CHARACTERISTICS cutting tools would be as follows: This of alloys is not hardenable by heat treatment. • End cutting edge angle - Approximately 7° They can be made harder through cold working only. The annealed hardness for these alloys is generally in the range • Nose Radius - Approximately .005” of RB 70/80, whereas the 1¦4 H to 1¦2 H range for this • Side cutting edge angle - Approximately 15° group of , can run between RB 80/96. Material in the annealed condition will be more difficult to machine because • Back rake - Approximately 8° it is soft and gummy. The tools tend to plow the instead • Side rake - Approximately 8° of cutting into it, and do not easily form chips. Surface scale When cutting off, high speed tools are better than carbide is tightly adherent and penetrates the surface to a tools, and a feed of approximately .001” per revolution should greater extent than stainless . Machining is considerably be used. The cutting tools should have a front clearance of improved by descaling the material. If there were standard about 7° and a fairly big tip - larger than 25° would be helpful. machinability ratings applied for this series of alloys, Alloy AISI-B-1112 being measured as 100%, the following percentages could be suggested for these chemistries:

INVAR 36 FM (ASTM F-1684) – 60% KOVAR (ASTM-F15) – 40% ALLOY 48 (ASTM F-30) – 40%

COOLANT It is important to control heat buildup, the major cause of warpage. Suggested coolants are Keycool 2000 or Prime Cut. Whatever lubricant is used for machining, it should not contain sulphur. Sulphur can effect the performance of many sealed electronic parts. DRILLING TOOLING When drilling a 3/16” diameter hole, a speed of about 40/ T-15 Alloy, such as Vasco Supreme - manufactured by FPM could possibly be used, and the feed should be about .002” Vanadium Alloys Company, M-3 Type 2 such as Van Cut Type to a .0025” per revolution, for a 1/2” hole, approximately the 2 - manufactured by Vanadium Alloys Company. same speed could be used with a feed of about .0040” to .005” per revolution. The drills should be as short as possible, and it For machining with carbide tools, a K-6 manufactured by is desirable to make a thin web at the point by conventional Kennemetal, Firthite HA manufactured by Firth Sterling, or methods. By conventional methods, we mean do not notch or #370 Carboloy could be used, or a K2S manufactured by make a crank shaft grind. It is suggested that heavy web type Kennemetal, or a Firthite T-04 manufactured by Firth Sterling drills with nitrided or electrolyzed surfaces be used. The hole, would be satisfactory. One thing of prime importance is that all of course, should be cleaned frequently in order to remove the feathered or edges should be removed from the tools. They chips, which will gall, and also for cooling. The drill should be should be kept in excellent condition by repeated inspection. ground to an included point angle of 118° to 120°. REAMING REAMING Reaming speeds should be half the drill speed, but the feed SIZE SFM FEED should be about three times the drill speed. It is suggested that the margin on the land should be about .005” to .010”, Under 1/2” 57 .0030 and that the chamfer should be .005” to .010” and the Over 1/2” 57 .0045 chamfer angle about 30°. The tools should be as short as possible, and have a slight face rake of about 5° to 8°. THREADING

TAPPING T.P.I. SFM In tapping, a tap drill slightly larger than the standard drill 3-7 1/2 8 recommended for conventional threads should be used, 8-15 10 because the metal will probably flow into the cut. It is suggested that on automatic machines, a two or three fluted Over 16 16 tapping tool should be used. For taps below 3/16”, the two fluted would be best. Grind the face hook angle to 8° to TAPPING 10°, and the tap should have a .003” to .005” chamfered T.P.I. SFM edge. If possible, if binding occurs in the hole in tapping, the 3-7 1/2 6 width of the land may be too great, and it is suggested that the width of the heel be ground down. Again, it is suggested 8-15 7 that nitrided or electolyzed tools be used. Speed should be 16-24 11 about 20/FPM. Over 25 16

HIGH SPEED TOOLS* BROACHING TURNING AND FORMING SFM FEED CUT-OFF TOOL SFM FEED 8-12 .001-.005 1/16” 65 .0010 TURNING SINGLE POINT & BOX TOOLS 1/8” 67 .0012 TOOLS SFM FEED 1/4” 69 .0016 High Speed 60-65 .0029 FORM TOOL SFM FEED Carbide 160-215 .025-.080 1/2” 67 .0012 1” 63 .0010 *When using carbide tools, surface speed feet/minute (sfm) can be 1 1/2” 63 .0009 increased between 2 and 3 times over the high speed suggestions. Feeds can be increased between 50 and 100%.NOTE: Figures used DRILLING for all metal removal operations covered are average. On certain work, the nature of the part may require adjustment of speeds and DRILL DIA SFM FEED feeds. Each job has to be developed for best production results with optimum tool life. Speeds or feeds should be increased or decreased in 3/8” 43 .0030 small steps.The information and data presented herein are typical or average values are not a guarantee of maximum or minimum values. 3/4” 45 .0036 Applications specifically suggested for material described herein are made solely for the purpose of illustration to enable the reader to MILLING make his own evaluation and are not intended as warranties, either SFM FEED express or implied, or fitness for these or other purposes. 35-70 .002-.005

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